【发布时间】：2018-07-02 13:26:17
【问题描述】：
我正在开发一个 android 应用程序，它需要定期检查可用的 wifi 列表，即使应用程序从后台被杀死也是如此。所以我正在考虑使用服务从后端检查它。在这种情况下，我在从服务中获取可用的 wifi 列表时遇到了一些问题。我在互联网上搜索，发现大部分仅针对活动的解决方案。虽然我试过了但没有用。
请注意。当我在直接活动中使用它们时，相同的代码也有效。但它在服务类中不起作用。
我的服务代码是.....
package com.example.sodrulaminshaon.ringmodecontroller;
import android.Manifest;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.content.pm.PackageManager;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import android.os.IBinder;
import android.os.SystemClock;
import android.preference.PreferenceManager;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import java.util.List;
import java.util.Set;
/**
* Created by Sodrul Amin Shaon on 22-Jun-18.
*/
public class MyService extends Service {
WifiManager wifiManager;
WifiReceiver receiverWifi;
private static final String LIST_TESTING = "ListTest";
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
SharedPreferences preferences = getSharedPreferences(Constants.PREFERENCE_NAME,MODE_PRIVATE);
boolean auto = preferences.getBoolean(Constants.AUTO_CONTROL_STR,false);
//if(MainActivity.getAutoControl())
if(auto)
{
wifiManager = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
if (!wifiManager.isWifiEnabled())
{
wifiManager.setWifiEnabled(true);
}
Log.i(LIST_TESTING,"Wifi is enabled. Now going to check the available list.");
receiverWifi = new WifiReceiver();
registerReceiver(receiverWifi,
new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
wifiManager.startScan();
}
stopSelf();
return START_STICKY;
}
class WifiReceiver extends BroadcastReceiver {
// This method call when number of wifi connections changed
public void onReceive(Context c, Intent intent) {
StringBuilder sb = new StringBuilder();
List<ScanResult> wifiList = wifiManager.getScanResults();
Log.i(LIST_TESTING,"Inside scan result receiver. Scan result size: "+wifiList.size());
sb.append("\n Number Of Wifi connections :"+wifiList.size()+"\n\n");
for(int i = 0; i < wifiList.size(); i++){
sb.append(new Integer(i+1).toString() + ". ");
sb.append(wifiList.get(i).SSID).toString();
sb.append("\n\n");
}
Log.i(LIST_TESTING,sb.toString());
}
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onDestroy() {
// I want to restart this service again in one hour
SharedPreferences preferences = getSharedPreferences(Constants.PREFERENCE_NAME,MODE_PRIVATE);
boolean auto = preferences.getBoolean(Constants.AUTO_CONTROL_STR,false);
if(auto)
{
if(wifiManager.isWifiEnabled())unregisterReceiver(receiverWifi);
AlarmManager alarm = (AlarmManager) getSystemService(ALARM_SERVICE);
alarm.set(
alarm.RTC_WAKEUP,
System.currentTimeMillis() + (1000 * 10),
PendingIntent.getService(this, 0, new Intent(this, MyService.class), 0)
);
}
}
}
无需担心权限问题。我在应用程序启动时获得了必要的权限。我仍然在分享参与的许可。
private void getPermission(){
if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED
&&
ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
askForLocationPermissions();
}
}
private void askForLocationPermissions() {
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
new android.support.v7.app.AlertDialog.Builder(this)
.setTitle("Location permessions needed")
.setMessage("you need to allow this permission!")
.setPositiveButton("Sure", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
LOCATION_PERMISSION_REQUEST_CODE);
}
})
.setNegativeButton("Not now", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
})
.show();
} else {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
LOCATION_PERMISSION_REQUEST_CODE);
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[], @NonNull int[] grantResults) {
switch (requestCode) {
case LOCATION_PERMISSION_REQUEST_CODE:
if (isPermissionGranted(permissions, grantResults, Manifest.permission.ACCESS_FINE_LOCATION)) {
} else {
Toast.makeText(this, "Can not proceed! i need permission" , Toast.LENGTH_SHORT).show();
}
break;
}
}
public static boolean isPermissionGranted(@NonNull String[] grantPermissions, @NonNull int[] grantResults,
@NonNull String permission) {
for (int i = 0; i < grantPermissions.length; i++) {
if (permission.equals(grantPermissions[i])) {
return grantResults[i] == PackageManager.PERMISSION_GRANTED;
}
}
return false;
}
我可以保证我的服务运行良好。它尝试每隔 10 秒检查一次可用的 wifi 列表。
我想知道的是。此代码无法打印可用的 wifi 列表。仅用于 MyService 类中的信息
Log.i(LIST_TESTING,"Wifi is enabled. Now going to check the available list.");
此行正在连续打印。但其他两行
Log.i(LIST_TESTING,"Inside scan result receiver. Scan result size: "+wifiList.size());
Log.i(LIST_TESTING,sb.toString());
没有被执行。谁能帮帮我....
【问题讨论】：
-
当你有不工作的代码，然后提出minimal reproducible example。我们不知道您读过什么，尝试过什么，以及为什么不起作用。所以请不要指望我们会重复之前写下的内容。您还应该在help center 上花一些时间来了解如何/在这里问什么。不是这样的。
-
嗨。感谢您的意见。我已经编辑了我的问题。请立即检查，看看您是否可以帮助我。当您将此问题标记为重复时，我向您保证此代码在活动中运行得很好。但不能在服务中工作。